Within the known types of machines, the assemblies intended for the preparation and the dispensing of beverages generally comprise a dispensing device having a seat receiving a single serve capsule.
Since the single serve capsules are originally sealed in order to prevent the soluble preparation from contacting the atmosphere and from leaking out during manipulation, the dispensing device is generally provided with a puncturing member or other means that opens one or more holes in at least one wall of the capsule, e.g. outlet holes on its bottom to provide an outlet for the beverage. In some cases an inlet hole for the liquid used to make the beverage (that is usually hot water) is also obtained at this step.
Once the capsule is positioned in the housing of the dispensing device and an exit for the beverage has been provided, hot pressurized water is fed to the capsule, through one or more inlet holes, to form a beverage, consisting of an infusion, dispersion or solution of the ground or soluble preparation in water. The beverage is then dispensed through the bottom outlet opening or hole. WO02/076270 discloses this type of embodiment.
Alternatively, as disclosed e.g. in EP 1243210, the capsule is located in its seat and pressurized hot water is fed inside the capsule to deform outwardly the bottom wall; a piston member pushes inwards a outlet lid provided on the bottom wall to form a permanent outlet for the beverage, the outlet lid being able to remain open also at the end of the dispensing step.
A good dispensing group must ensure complete and uniform solubilisation (or suspension/dispersion) of the whole product or of those parts of the product that upon brewing or infusion are solubilized into the hot water and a good final appearance of the beverage; for coffee and cappuccino, a good final appearance means having a “froth”, i.e. a layer of foam made of small bubbles, which is lasting and in an appreciable amount. This result is difficult to obtain because the shape and size of the capsules are the same for all the dispensable products, whereas the amount of soluble product provided within a capsule changes according to its nature. For example, 1.5 grams of product are provided when the beverage to be dispensed is espresso coffee from a soluble espresso preparation, about 3.0 grams for tea leaves, about 6.5 grams when the product is ground coffee, and 15-16 grams, or more, of product are provided within the same capsule when the beverage is soluble hot-chocolate or cappuccino. This difference in quantities is reflected in the possible difficulty in consistently obtaining the required amount and quality of foam for each beverage.
Another problem with the known dispensing groups, particularly when milk-based soluble products are treated, is to ensure the hygiene of the group; this results into the requirement of avoiding the presence of small-sized cross-sectioned supply conduits and tubes (less than about 2 mm) because films and residues may be formed therein. Unfortunately, it appears that these small-sized conduits may be very useful to provide the required foam.
Previously mentioned patent application WO02/076270 in the name of the same applicant (incorporated herein by reference) describes a dispensing assembly wherein the puncturing member or piston acts as a means of opening a substantially circular portion on the capsule bottom. The diameter ratio of the piston and circular portion on the capsule bottom results in a throttling enabling to achieve good dispensing and production of foam or “froth”.
It has however been observed that variations in the results are obtained depending on the products and the doses used and hence a need exists of having uniform results with the above described dispensing groups.
US Pat. Appl. 2003/00056661 to Hu et. al. and the corresponding application WO 02/080744 (corresponding to above mentioned EP 1243210) to Societé des Produits Nestlé describe a soluble product dispensing method wherein the outlet lid element open by the puncturing member is plastically deformed in such a position as to create a passage having reduced dimensions, i.e. a throttling, for the liquid outflow from the capsule. These dimensions remain constant over time while dispensing the beverage and at the end of the dispensing step the lid is open. In order to improve the formation of foam, the puncturing member is provided with channels having a cross section of less than 2 mm; alternatively, the channels are formed on the capsule, between two adjacent walls and in contact therewith.
This embodiment has drawbacks in that it does not operate in a reproducible and constant way and suffers from the above described problems regarding the blockage of the channels and their possible contamination with bacteria due to the formation of films and accumulations of residues within the channels. Furthermore, the capsule is complex and expensive to manufacture in view of the way the outlet lid is obtained within the bottom wall.
Therefore, a need exists for an improved beverage dispensing system, particularly for soluble beverages, which allows to obtain the required beverage and the required amount of foam, in a simple, hygienic and economical way.